Casting aluminum alloy with dispersed cnt and method for producing the same

ABSTRACT

The present disclosure provides a casting aluminum alloy with dispersed carbon nanotubes (CNT), which is molded by charging an oxide-coated CNT in the range of 1 to 5 vol % into a molten Al—Ti—B-based alloy, and stirring the resulting mixture. The aluminum alloy has enhanced elasticity by forming a TiB 2  compound in a structure, and a method for producing the same.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. §119(a) the benefit of Korean Patent Application No. 10-2011-0122884 filed on Nov. 23, 2011, the entire contents of which are incorporated herein by reference.

BACKGROUND

(a) Technical Field

The present disclosure relates to a casting aluminum alloy with dispersed high elastic casting carbon nanotubes for mass production, and a method for producing the same.

(b) Background Art

Carbon nanotubes (CNT) are a micro-molecule having a long-tube shape formed by carbons linked to a six-membered ring structure, and a diameter of 1 nanometer (1 nanometer is equal to one billionth of 1 meter). CNT are so named because a carbon sheet formed by linking 3 carbon atoms to a honeycomb structure is rolled into a tube shape.

CNT are a new material having the tension force one hundred times stronger than a steel, and excellent flexibility. Because CNT are hollow, they are very light. Additionally, CNT have good electrical conductivity (as good as copper) and good thermal conductivity (as good as a diamond).

CNT were first identified in 1991, by Dr. Ijima of NEC research institute in Japan, who found a tube-type carbon molecule while looking through a microscope.

After it was found that CNT have a property of being a conductor or semiconductor according to the diameter of its tube, it came to the forefront of research and development as a next generation semiconductor material. Additionally, CNT can be used as a semiconductor memory device, hydrogen storage, hydrogen battery electrode, and the like because of having various properties according to shapes of a single-walled tube, multi-walled tube, bundle and the like.

For example, a semiconductor chip prepared with CNT can obtain a degree of integration of tera (1 trillion) bites, exceeding the current limit of giga (1 billion) bites. CNT can be used as a battery by storing hydrogen in empty tubes, or a high-purity purification filter. Because CNT can absorb anything, even radar waves, there is a trend to develop a CNT based aircraft paint suitable for stealth aircraft, to aid their ability to avoid detection by a monitoring network.

Unfortunately, the development of CNT composites has been difficult. For example, it is difficult to disperse large quantities of CNT due to the effect of CNT agglomeration, which causes non-uniform dispersion of the CNT. Additionally, attempts to develop such composites have been based on a CNT powder molding process, which has proven to be cost prohibitive for mass production.

Conventionally, a reinforced aluminum alloy of a metal-based compound, a CNT dispersed aluminum composite, and the like have been produced, but the improvement of the elasticity was insufficient, typically displaying 100 GPa or less, as comparing with a cast-iron elasticity of 120 GPa. Furthermore, when producing a CNT composite, it was difficult to disperse CNT at an amount of more than 5 vol % due to the non-uniform dispersion caused by CNT agglomeration.

Accordingly, there is a need in the art for an alloy with dispersed CNT.

SUMMARY OF THE DISCLOSURE

The present invention provides a high elastic casting aluminum alloy for improving the rigidity and noise, vibration, harshness (NVH) characteristic and mass production.

A casting aluminum alloy with dispersed CNT according to an exemplary embodiment of the present invention is molded by charging an oxide-coated CNT 1 to 5 vol % into a molten Al—Ti—B-based alloy and stirring, thereof, and has enhanced elasticity by forming a TiB₂ compound in a structure. The molten Al—Ti—B-based alloy can be formed by mixing/stirring a molten Al—Ti-based alloy and a molten Al—B-based alloy by an in-situ method. The Al—Ti-based alloy can comprise Ti 2 to 7 wt %, and the Al—B-based alloy can comprise B 1 to 3 wt %.

According to an exemplary embodiment of the invention, a method for producing a casting aluminum alloy with dispersed CNT includes a molten metal forming step of forming a matrix molten metal by mixing/stirring a molten Al—Ti-based alloy and a molten Al—B-based alloy by an in-situ method; and a charging step of charging an oxide-coated CNT 1 to 5 vol % into the formed molten metal and stirring thereof. In the molten metal forming step, the molten Al—Ti-based alloy comprising Ti 2 to 7 wt % and the molten Al—B-based alloy comprising B 1 to 3 wt % can be mixed. In the molten metal forming step, a TiB₂ compound can be formed in the structure by mixing/stirring by in-situ method.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated by the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a graph representing the increase of the modulus of the elasticity according to the dispersion increase of CNT of the casting aluminum alloy with dispersed CNT of an exemplary embodiment of the present invention; and

FIG. 2 is graph representing the increase of the modulus of the elasticity by the CNT dispersion in a boride compound reinforced matrix of the casting aluminum alloy with dispersed CNT of an exemplary embodiment of the present invention.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Hereinafter reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.”

Ranges provided herein are understood to be shorthand for all of the values within the range. For example, a range of 1 to 50 is understood to include any number, combination of numbers, or sub-range from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all intervening decimal values between the aforementioned integers such as, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. With respect to sub-ranges, “nested sub-ranges” that extend from either end point of the range are specifically contemplated. For example, a nested sub-range of an exemplary range of 1 to 50 may comprise 1 to 10, 1 to 20, 1 to 30, and 1 to 40 in one direction, or 50 to 40, 50 to 30, 50 to 20, and 50 to 10 in the other direction.

It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

Hereinafter, a casting aluminum alloy with dispersed CNT and a method for producing the same according to the preferred embodiments of the present invention now will be described in detail with reference to the accompanying drawings.

The casting aluminum alloy with the dispersed CNT according to an exemplary embodiment of the present invention is molded by charging an oxide-coated CNT 1 to 5 vol % into a molten Al—Ti—B-based alloy and stirring thereof, thereby forming a TiB₂ compound in the structure so as to improve the elasticity.

Conventionally, a reinforced aluminum alloy of a metal-based compound, a CNT dispersed aluminum composite, and the like have been produced, but the improvement of the elasticity was insufficient, for example, an elasticity of 100 GPa or less as compared to cast-iron (120 GPa). Further, when producing the CNT composite, it was difficult to disperse CNT to the amount of more than 5 vol % due to the non-uniform dispersion caused by CNT agglomeration, and the like. Additionally, there were limits of the cost competitiveness and productivity because it was produced by a powder molding process.

According to an exemplary embodiment of the present invention, it is possible to secure an elasticity coefficient of 120 GPa (i.e., an equivalent level to that of cast-iron) by dispersing CNT to the amount of 5 vol % or less to an aluminum matrix, wherein a boride compound is formed, thereby maximizing the improvement of elasticity. An aluminum matrix alloy is prepared to improve the elasticity. In order to prepare the boride compound (TiB₂:541 GPa), the preferred compound for improving elasticity, a molten casting matrix alloy using Al—Ti and Al—B master alloys is prepared. Using aluminum master alloys of Al-(2 to 7 wt %)Ti and Al-(1 to 3 wt %)B, the formation of TiB₂ can be induced by in-situ reaction, not by power type injection (to obtain material uniformity), and the first matrix elasticity coefficient can be secured to the level of 100 GPa.

Furthermore, the oxide-coated CNT 1 to 5 vol % for preventing oxidization at high temperature is added into the molten metal. Because CNT are oxidized by being reacted with oxygen at high temperature, in order to prevent this, the CNT were coated with an oxide such as, for example, SiO₂, charged into the molten metal, and stirred.

As a result, the elasticity coefficient increased (up to 120 GPa or more, equivalent level to that of cast-iron) due to the TiB₂ phase of the matrix alloy and the CNT were dispersed through an in-situ reaction; consequently, the amount of CNT can be minimized by increasing the elasticity coefficient of the matrix itself so as to increase the cost reduction. Additionally, the productivity can be improved by producing the casting-based composite, rather than the existing power molded CNT composite.

According to an exemplary embodiment of the invention, the molten Al—Ti—B-based alloy can be formed by mixing/stirring the molten Al—Ti-based alloy and the molten Al—B-based alloy by an in-situ method, and the molten Al—Ti-based alloy can comprise Ti 2 to 7 wt % and the molten Al—B-based alloy can comprise B 1 to 3 wt %.

According to an exemplary embodiment, the method for producing the casting aluminum alloy with dispersed CNT according to the present invention includes: a molten metal forming step of forming a matrix molten metal by mixing/stirring a molten Al—Ti-based alloy and a molten Al—B-based alloy by an in-situ method; and a charging step of charging an oxide-coated CNT 1 to 5 vol % into the formed molten metal and stifling thereof.

Herein, in the molten metal forming step, the molten Al—Ti-based alloy comprising Ti 2 to 7 wt % and the molten Al—B-based alloy comprising B 1 to 3 wt % can be mixed, and in the molten metal forming step, the TiB₂ compound can be formed in the structure by mixing/stirring by in-situ method.

Following Table 1 is a chemical composition of the high elastic casting alloy using the boride compound, and Table 2 represents the increase of the elasticity coefficient according to the increase of TiB₂ phase.

TABLE 1 Chemical Composition (wt %) TiB₂ Al Ti B Production (wt %) 1 96.7 2.3 1 3.21 2 93.5 4.5 2 6.3 3 90.6 6.5 2.9 9.32

TABLE 2 TiB₂ (wt %) Elasticity Coefficient (Gpa) 3.21 77.9 3.6 87.7 9.32 98

As shown in the Tables, it is confirmed that the elasticity coefficient significantly increases according to the increase of the TiB₂ production.

FIG. 1 is a graph representing the increase of the modulus of the elasticity according to the increase in the dispersion of CNT of the casting aluminum alloy, and it indicates that the elasticity coefficient of the composite increased according to the increase of CNT vol % through a Voigt-Reuss model. Particularly, the elasticity coefficient increased to 92 GPa when dispersing CNT 5 vol % as an experimental threshold value.

FIG. 2 is graph representing the increase of the modulus of the elasticity by the CNT dispersion in a boride compound reinforced matrix of the casting aluminum alloy with dispersed CNT of an exemplary embodiment of the present invention. FIG. 2 confirms that the elasticity coefficient increase from 68 to 98 GPa by the matrix alloy wherein TiB₂ was produced to 9.32 wt %. Furthermore, the elasticity coefficient due to the CNT dispersion increased from 98 to 122 GPa in the boride compound aluminum matrix, and therefore, the elasticity coefficient of 122 GPa can be secured when dispersing CNT to 5 vol %.

According to the casting aluminum alloy with dispersed CNT and the method for producing the same consisting of the structure described above, the elasticity coefficient increases (120 GPa or more, equivalent level to the cast-iron) due to the TiB₂ phase of the matrix alloy and the dispersed CNT through in-situ reaction. Further, due to the improvement of the elasticity coefficient of the matrix itself, the amount of the CNT can be minimized and therefore, the cost can be significantly reduced. And, the productivity can be improved by producing the casting-based composite, not the existing power molded CNT composite.

While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 

What is claimed is:
 1. A casting aluminum alloy, comprising: carbon nanotubes (CNT), wherein the CNT are oxide coated and present in the range of 1 to 5 vol %; and an Al—Ti—B alloy, wherein the CNT are evenly dispersed throughout the Al—Ti—B alloy.
 2. The casting aluminum alloy of claim 1, wherein the Al—Ti—B-based alloy is formed by mixing/stirring a molten Al—Ti-based alloy and a molten Al—B-based alloy by an in-situ method.
 3. The casting aluminum alloy of claim 2, wherein the Al—Ti-based alloy comprises Ti in the range of 2 to 7 wt %.
 4. The casting aluminum alloy of claim 2, wherein the Al—Ti-based alloy comprises Ti at about 2 wt %.
 5. The casting aluminum alloy of claim 2, wherein the Al—Ti-based alloy comprises Ti at about 3 wt %.
 6. The casting aluminum alloy of claim 2, wherein the Al—Ti-based alloy comprises Ti at about 4 wt %.
 7. The casting aluminum alloy of claim 2, wherein the Al—Ti-based alloy comprises Ti at about 5 wt %.
 8. The casting aluminum alloy of claim 2, wherein the Al—Ti-based alloy comprises Ti at about 6 wt %.
 9. The casting aluminum alloy of claim 2, wherein the Al—Ti-based alloy comprises Ti at about 7 wt %.
 10. The casting aluminum alloy of claim 2, wherein the Al—B-based alloy comprises B in the range of 1 to 3 wt %.
 11. The casting aluminum alloy of claim 2, wherein the Al—B-based alloy comprises B at about 1 wt %.
 12. The casting aluminum alloy of claim 2, wherein the Al—B-based alloy comprises B at about 2 wt %.
 13. The casting aluminum alloy of claim 2, wherein the Al—B-based alloy comprises B at about 3 wt %.
 14. A method for producing the casting aluminum alloy of claim 1 comprising: (a) forming a molten Al—Ti-based alloy; (b) forming a molten Al—B-based alloy; (c) mixing the molten Al—Ti-based alloy and the molten Al—B-based alloy by in-situ method; (d) charging an oxide-coated CNT into the resulting molten metal, wherein the CNT are present in the range of 1 to 5 vol %, and (e) stirring the charged molten metal.
 15. The method of claim 14, wherein the molten Al—Ti of step (a) comprises Ti in the range of about 2 to 7 wt %.
 16. The method of claim 14, wherein the molten Al—B of step (b) comprises B in the range of about 1 to 3 wt %.
 17. The method of claim 14, wherein step (c) forms a TiB₂ compound in a structure by mixing/stirring by in-situ method. 